biological differences

Except for that everybody is different and everybody has a different personality, which counts for animals as much as for us, there are perhaps also species specific distributions of what different species might like/prefer or tolerate more or less when being passively or actively mating with...

An interesting argument came up on another thread about a lady that's possibly a MtF (male-to-female) trans, but I'm unsure as to what the differences would be like anatomically speaking. Obviously, males and females have different builds from each other, but with so little experience I...